The manganacarborane dianion in [N(PPh3)(2)][NEt4][1,1,1-(CO)(3)-2-Ph-c/oso-1,2-MnCBgHg] (1b) reacts with cationic transition metal-ligand fragments to give products in which the electrophilic metal groups (M') are exo-polyhedrally attached to the {closo-1,2-MnCB9} cage system via three-center two-electron B-H -> M' linkages and generally also by Mn-M' bonds. With {Cu(PPh3)}(+), the Cu-Mn-Cu trimetallic species [1,6-{Cu(PPh3)}-1,7-{Cu(PPh3)}-6,7-(mu center dot H)(2)center dot 1,1,1-(CO)(3)-2-Ph-c/oso-1,2-MnCBgH7] (3a) is formed, whereas reactions with {M'(dppe)}(2+) (M' = Ni, Pd; dppe = Ph2PCH2CH2PPh2) give [1,3-{Ni(dppe)-3-(mu center dot H)-1,1,1-(CO)(3)-2-Ph-c/oso-1,2-MnCB9H8] (5a) and [1,3,6-{ Pd(dppe)}-3,6-(mu-H)(2)-1,1,1-(CO)(3)-2-Ph-c/oso-1,2-MnCB9H7] (5b), both of which contain M'-Mn bonds. The latter reaction with M' = Pt affords [3,6-fPt(dppe)1-3,6-(mu-H)(2)-1,1,1-(CO)(3)-2-Ph-c/oso-1,2-MnCB9H7] (6), which lacks a Pt-Mn connectivity. Compound 6 itself spontaneously converts to [1-Ph-2,2,2-(CO)(3)-8,8-(dppe)-hyperc/oso-8,2,1-PtMnCBgHg] (7b) and thence to [3,6,7-{Mn(CO)(3)}-3,7 (mu-H)(2)-1-Ph-6,6-(dppe)-c/oso-6,1-PtCB8H6] (8). This sequence occurs via initial insertion of the {Pt(dppe)} unit and then extrusion of {Mn(CO)(3)} and one {BH} vertex. In the presence of alcohols ROH, compound 6 is transformed to the TOR substituted analogues of 7b. X-ray diffraction studies were essential in elucidating the structures encountered in compounds 5-8 and hence in understanding their behavior.